| 摘要 |
PURPOSE:To inhibit the quantity of warpage of the non-suction section of a substrate in the same extent as a suction section even in the non-suction section by previously making the pitches of projecting sections in the peripheral section of a suction surface smaller than other sections. CONSTITUTION:An opening section 1a to which suction force does not work is formed at the central section of a wafer holder 1. The pitch of the annular projecting section 10a of an outermost circumference and an annular projecting section 10b on the inside of the projecting section 10a and the pitch of an annular projecting section 10g in the periphery of the opening section and an annular projecting section 10f on the outside of the projecting section 10g are represented by l2 and the pitches of other mutual adjacent annular projecting sections by l1, and these pitches are determined so as to satisfy l2/l1<1/1.2. The width in the radial direction of the upper end faces of each annular projecting section 10a-10g may be reduced extremely in order to diminish the probability of the placing of dust resulting in the deterioration of flatness at that time. Since the quantity of warpage of the peripheral section of the suction surface of a substrate is proportional to the fourth power of the pitches of the projecting sections in consideration of fine width, the pitches of the projecting sections in the peripheral section of the suction surface is previously made smaller than other sections, thus inhibiting the quantity of warpage of the non-suction section of the substrate in the same extent as a suction section even in the non-suction section. |
